Effects of hormone replacement therapy on cerebral serotonin-1A receptor binding in postmenopausal women examined with [carbonyl-11C]WAY-100635

Preclinical research points to a strong modulatory influence of gonadal hormones on the serotonin system. However, human data corroborating this association remains scarce. The aim of this study was to examine the effects of hormone replacement therapy on 5-HT1A receptor binding in postmenopausal women using positron emission tomography (PET) and the radioligand [carbonyl-C-11]MAY-100635. In this randomized, double-blind, longitudinal study, 30 postmenopausal women underwent treatment with either a combination of oral 17 beta-estradiol valerate and micronized progesterone (group 1, n = 10), oral 17 beta-estradiol valerate (group 2, n = 10), or placebo (group 3, n = 10). Two PET measurements were performed, one the day before treatment start and the second after at least eight weeks of treatment. Plasma levels of estradiol (E-2) progesterone (P-4), sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), follicle stimulating hormone (FSH) and luteinizing hormone (LH) were collected prior to PET measurements. As expected, hormone replacement therapy led to a significant increase in E-2 and P-4 plasma levels in group 1 and to a significant increase in E-2 levels in group 2. The 5-HT1A receptor binding did not change significantly after estrogen, combined estrogen/progesterone treatment or placebo in any of the investigated brain regions. There were no significant correlations between changes in E-2 or P-4 values and changes in 5-HT1A receptor binding. Although we were not able to confirm effects of gonadal hormone treatment on 5-HT1A receptor binding, our data do not preclude associations between sex steroid levels and serotonin, the neurotransmitter implicated most strongly in the pathogenesis of affective and anxiety disorders. (C) 2014 Elsevier Ltd. All rights reserved.